1. Field of the Invention
The present invention relates to a liquid joint process for joining of an electrical contact and a carrier.
2. Description of the Prior Art
An electrical contactor comprising a carrier made of a copper alloy and an electrical contact made of Ag-CdO material, or Ag-SnO.sub.2 -In.sub.2 O.sub.3 material has been used in a magnet switch and a nofuse breaker etc.
Such an electrical contactor is illustrated in FIG. 1.
In the preparation of such electrical contactor which should have high disconnection resistance and high fusion resistance, a brazing process is employed for joining of an electrical contact (1) and a carrier (3) as shown in FIG. 1.
When a clad silver layer (2) is formed on the joint surface of the electrical contact (1) and then, a brazing material and flux are fed between the silver layer and a carrier (3) in a brazing work item, brazing is attained between the clad silver layer (2) and the carrier (3) to form a fillet (4) around the electrical contact (1) and the carrier (3). However many voids (6) are formed in the brazing part (5). It is considered that a joint area coefficient between the contact (1) and the carrier (3) is in a range of 60 to 70%.
In order to overcome such disadvantages and to save brazing material, flux etc., various brazing process have been proposed. In view of the joint area coefficient and the life of the contactor, such proposed brazing process results in inferior quality versus those of the joint process for the contactor by the above-mentioned brazing process. Therefore, these processes have not been practically employed. For example, it has been proposed to form the clad silver layer (2) on the surface of the contact (1) and then to weld the contact (1) and the carrier (3) by resistance-heating as shown in FIG. 2 (A), (B). That is, the contact (1) having the clad silver layer (2) and the carrier (3) made of a copper alloy are held by an upper electrode (7) and a lower electrode (8) and are welded by feeding current to heat them. In such process, the cald silver layer (2) and the carrier (3) are partially fused in the joint part (9) to form an alloy and the alloy is scattered out of the peripheral part of the contact (1) to form a burr (10). The burr (10) causes remarkable deterioration of the fusion resistance and the life. Moreover, a burn-stick or fusion is easily caused between the upper electrode (7) and the contact (1) or between the lower electrode (8) and the carrier (3) to cause inferior workability.